1. Field of the Invention
The present invention relates to an expansion valve including a temperature sensing mechanism used in a refrigeration cycle.
2. Description of the Related Art
In a refrigeration cycle used in air conditioning devices or the like provided in automobiles, a temperature expansion valve including a temperature sensing mechanism that adjusts an amount of passing refrigerant according to temperature has been used for saving an installation space and wiring.
FIG. 4 is a sectional view of an example of a conventional expansion valve including a temperature sensing mechanism. In a valve body 30, a first passage 32 and a second passage 34 are formed vertically spaced apart from each other, the first passage 32 being a passage for a high pressure liquid refrigerant having condensed by a condenser 5 and passed through a receiver 6, and the second passage 34 being a passage through which a gas phase refrigerant supplied from a refrigerant outlet of an evaporator 8 to a refrigerant inlet of a compressor 4 flows. Reference numeral 11 denotes piping.
The first passage 32 includes an inlet port 321 through which the liquid refrigerant is introduced, a valve chamber 35 communicating with the inlet port 321, a valve hole 32a provided in the valve chamber 35, and an outlet port 322 through which the refrigerant expanded in the valve hole 32a is discharged to the outside. A valve seat is formed at an inlet of the valve hole 32a, and a valve member 32b is placed to face the valve seat. The valve member 32b is biased toward the valve seat by a compression coil spring 32c. A lower end of the valve chamber 35 opens in a bottom surface of the valve body 30, and the opening is sealed by a plug 37 screwed into the valve body 30.
To an upper end of the valve body 30, a valve member driving device 36 for driving the valve member 32b is mounted. The valve member driving device 36 includes a pressure operating housing 36d having an inner space partitioned by a diaphragm 36a into two upper and lower pressure operating chambers 36b and 36c. The lower pressure operating chamber 36c in the pressure operating housing 36d communicates with the second passage 34 via a pressure equalizing hole 36e formed concentrically with the centerline of the valve hole 32a. A pressure of the gas phase refrigerant in the second passage 34 is applied to the lower pressure operating chamber 36c via the pressure equalizing hole 36e. 
In the pressure equalizing hole 36e, a valve member driving rod 36f extending from a lower surface of the diaphragm 36a to the valve hole 32a formed with respect to the first passage 32 is placed concentrically with the pressure equalizing hole 36e. The valve member driving rod 36f is vertically slidably guided by a slide guide hole provided in a partition portion between the first passage 32 and the second passage 34 in the valve body 30, and a lower end of the valve member driving rod 36f abuts against the valve member 32b. To the partition portion, a seal member 36g is mounted that prevents leakage of the refrigerant between the first passage 32 and the second passage 34.
The upper pressure operating chamber 36b in the pressure operating housing 36d is filled with a known diaphragm driving fluid, to which heat of the gas phase refrigerant flowing through the second passage 34 is transferred via the valve member driving rod 36f located in the second passage 34 and the pressure equalizing hole 36e and the diaphragm 36a. The diaphragm driving fluid in the upper pressure operating chamber 36b is gasified by the transferred heat, and a pressure of the gas is applied to an upper surface of the diaphragm 36a. The diaphragm 36a is vertically displaced according to differences between the pressure of the diaphragm driving gas applied to the upper surface of the diaphragm 36a and the pressure applied to the lower surface thereof. The vertical displacement of the central portion of the diaphragm 36a is transmitted to the valve member 32b via the valve member driving rod 36f, and the valve member 32b is brought close to and apart from the valve seat at the valve hole 32a. This controls a flow rate of the refrigerant flowing toward the evaporator 8. Japanese Patent Laid-Open Publication No. 2002-054861 discloses an expansion valve having a similar structure, in which a heat transfer delay member is housed in a valve member driving rod to prevent hunting of a valve member.